Strut type and double wishbone type wheel suspension systems are mostly widely used as vehicle independent wheel suspension systems. The linear arrangement incorporating a coil spring and a damper (shock absorber) for damping the oscillation in a coaxial relationship is mostly widely used in such wheel suspension systems (Japanese utility model laid open publication (kokai) No. 3-43005 and others). The damper typically consists of a hydraulic telescopic shock absorber.
A conventional linear arrangement of a damper and a coil spring was however detrimental in improving the comfort of the rear seats and increasing the capacity of the luggage compartment because the axial dimension was so large that a part of the damper or the spring inevitably protruded into the passenger compartment or the luggage compartment.
In such a wheel suspension system, if the rear wheel is steered inward with respect to the turning circle of the vehicle, the side slip angle of the vehicle body for achieving a required slip angle of the rear wheel can be reduced so that the onset of the cornering force when starting a turn is advanced, and the steering response improves. It is also desirable to steer the outer rear wheel of a turning vehicle, which is required to bear a larger load, in a toe-in direction when a brake is applied thereto because it improves the controllability of the attitude of the vehicle at the time of brake application during a turn. To achieve such a goal, there has been proposed a wheel suspension system including lateral links disposed in a trapezoidal arrangement as seen from above with the aim of increasing the toe-in angle when making a turn or applying a brake.
However, according to such a conventional arrangement, it was necessary to provide a means to accommodate the change in the toe angle of the wheel in the part for connecting the lateral link to the knuckle or the vehicle body. Typically, the rubber bush in the connecting part was given with a high compliance to accomplish this goal. However, if the rubber bush is too compliant, the steering response tends to be impaired, and a desired firmness in the steering response may not be achieved. In particular, the proper tuning of the compliance of the rubber bush was highly difficult to achieve.